1. Field of the Invention
The present invention relates to airbags, and more specifically, to an apparatus and method for fastening a load plate to an airbag.
2. Technical Background
The introduction of airbags over the past several decades has prevented numerous deaths and injuries. Some estimates place the number of lives saved by airbags in excess of 10,000 per year. The most common type of airbag is the dashboard mounted airbag. Dashboard mounted airbags may be positioned in the steering wheel or in the dashboard directly in front of the passenger. When a vehicle experiences a sudden deceleration, an inflator rapidly inflates the airbag with a gas. These airbags prevent the occupants from striking the rigid portions of the dashboard.
While such airbags are credited with saving many lives, dashboard mounted airbags do not prevent all injuries that may occur during an automobile accident. In an effort to protect occupants from other areas of a vehicle not protected by a dashboard mounted airbag, multiple airbags and inflatable curtains are being positioned throughout the interior of vehicles. Overhead inflatable curtains and under dashboard knee airbags are now being employed in multiple vehicles to not only save lives but to allow other restraining devices to operate more effectively.
For example, during a front end collision, if the occupant is restrained by a seat belt, the occupant's upper torso bends at the waist and hits the primary airbag. However, depending on the design of the vehicle seat and force of the collision, there is a tendency for an occupant to slide forward along the seat and slip below the primary airbag, falling to the feet and leg compartment of the vehicle. The tendency is pronounced when the occupant is not properly restrained by a seat belt. Sliding of the occupant below the primary airbag is referred to as “submarining.” When the occupant submarines, the primary airbag is less effective in protecting the occupant. Submarining is but one example of instances where extra support is needed to protect occupants or goods in an accident situation.
In order to prevent submarining in vehicles, a knee airbag system has been developed. The goal of the knee airbag system is, during an accident, to position a piece of rigid material similar to the material of the instrument panel close to the occupant's knees and legs creating leg and knee support, which prevents submarining. The knee airbag system allows a vehicle manufacturer to design vehicles with more leg room and still have safety comparable to that of vehicles with less leg room. To accomplish the goal, the knee airbag system, when deployed, is typically coupled to an expanding cushion, which positions a portion of the instrument panel in a position to restrict the occupant's forward movement.
Unfortunately, several design concerns must be addressed in order to effectively employ knee airbags. For example, knees may induce two concentrated forces that are focused on a generally small area. When knees impact a typical airbag, the airbag will simply displace the gas within the airbag away from the knees. Thus, despite the presence of an airbag, the occupant's knees may still strike the structure behind the airbag, resulting in injury.
In order to prevent the concentrated force of a knee from displacing the gas in an airbag, force distributing load plates are being attached to airbags. A load plate is a generally rigid plate that is attached to the front of an airbag. When a concentrated force is applied to the load plate, the load plate will transfer that force across the entire airbag. Thus, knees impacting the load plate will be cushioned by the entire airbag.
However, attaching a load plate to an airbag has various design problems. For example, the load plate must remain attached to the airbag as the airbag rapidly inflates. In many airbag systems, the airbag is rapidly inflated by a high pressure gas ejecting from an inflator. The high pressure gas deploys the airbag and the associated load plate toward the occupant. Some airbags propel the load plate at a speed in excess of 100 mph and the, making a secure attachment essential. Such high speeds require an attachment mechanism that can withstand the high forces associated with a rapid acceleration and deceleration.
Furthermore, traditional fasteners such as screws or rivets may not be preferable for knee airbag applications. Drawback to screws and rivets is the number of parts and assembly procedures. Both screws and rivets require two attaching members, which can be difficult to assemble and can also increase the size of the module. Furthermore, rotating a screw numerous times or implementing a rivet gun for each attachment location can be time consuming and increase manufacturing capital expenses.
Therefore, what is needed is a force distributing airbag module that provides a simple attachment mechanism for attaching a load plate to an airbag. The attachment mechanism should be capable of receiving a large impulse force produced by a deploying airbag. The attachment mechanism should also have a limited number of parts and a generally low profile. What is also needed is a method for attaching a load plate to an airbag requiring minimal steps, while maintaining a generally strong attachment. Such apparatuses and methods are disclosed and claimed herein.